Enhanced Formation of Dicarboxylic Acids in the Catalytic Oxidation of Polyethylene With O₂ and NO_x

A promising strategy to valorize polyethylene is its oxidation to dicarboxylic acids with O₂ and NO_x. However, it remains unclear whether and how the formation of dicarboxylic acids from polyethylene can be increased through catalyst design and reaction parameters adjustment. In this work, it was found that through proper reaction condition selection and in the absence of a catalyst the yield toward dicarboxylic acids could reach ∼29 mol% with only little overoxidation to undesired CO and CO₂. At high NO partial pressure, the formation of gaseous products is suppressed, yielding an excellent carbon recovery for a variety of polyethylene types. The yield toward dicarboxylic acids can be further enhanced through the addition of a Cu²⁺/V⁵⁺ catalyst up to ∼51 mol% (>90% wt.% diacid), while the excellent carbon recovery can be maintained. It was found that the catalyst system was both robust and tolerant as the use of post-consumer plastic waste, a mixture of polyethylene and polypropylene, yielded a similar product slate.